原文
Pathology

The urachus is usually composed of three layers: an outer muscular layer, a middle layer of connective tissue and the innermost layer, which is usually lined with transitional epithelium. Although the lumens of urachal remnants passing through the bladder wall are most frequently covered with normal-appearing transitional cell epithelium, urachal cancers are nearly always adenocarcinomas. Only rarely have sarcomatoid, squamous or transitional cell elements been reported. These adenocarcinomas display an enteric-type histology more frequently associated with colorectal cancer. These tumors often have glandular structures and mucin production, and may also have colloid and/or signet-ring cell histology present.

Although the origin of these adenocarcinomas is not definitively known, two theories have been proposed regarding their development. Explaining their close resemblance to colorectal cancer is the theory that these tumors originate from

enteric rests left behind from the cloaca during embryological development. An alternative hypothesis is that these tumors result from a metaplastic pathway. Evidence supporting the latter includes the development of adenocarcinomas in the renal pelvis and ureter, which are not of cloacal origin, observations of adenocarcinoma arising from cystitis glandularis and the occurrence of adenocarcinomas in extrophic bladders despite transitional cell epithelium at birth.

譯文
病理學(xué)

臍尿管通常是由三層組成：外層肌肉層，中間結(jié)締組織層和最內(nèi)層（通常是移行上皮）。

雖然臍尿管殘余腔穿過膀胱壁，經(jīng)常被看似正常的移行細(xì)胞上皮覆蓋，但臍尿管癌幾乎都是腺癌。據(jù)報(bào)道只有極少部分為肉瘤樣、鱗狀或移行細(xì)胞癌。這些腺癌顯示腸型組織更常與結(jié)直腸癌有關(guān)。這些腫瘤常有腺體結(jié)構(gòu)和粘蛋白的產(chǎn)生，還可能有膠狀和/或印戒細(xì)胞組織存在。

雖然這些腺癌來(lái)源不是很確定，但是針對(duì)這些腫瘤的發(fā)展提出了兩個(gè)理論。解釋和結(jié)直腸癌癥非常相似的理論是，這些腫瘤起源于胚胎發(fā)生期間泄殖腔的腸內(nèi)皮靜息細(xì)胞左后側(cè)。另一種理論是，這些腫瘤來(lái)源于轉(zhuǎn)化途徑。支持后者的證據(jù)包括腎盂和輸尿管處腺癌的形成（而不是源于泄殖腔），以及盡管出現(xiàn)移行細(xì)胞上皮但是觀察到源于腺性膀胱炎的腺癌和出現(xiàn)外生膀胱腺癌。